Fired the kiln again with the 3.7 volt battery powering the Max chip. Worked as expected. However it made no difference to the intermittent readings at high temp. Don't know what to try next. The problem has appeared only above 1600 F. It has been the same with different wire to the probe ,I added a 2200 uf capacitor across 5 volt supply , then a battery to the chip...no change to this problem. I still can function with it like this and I am getting very good results with the kiln. Would be nice to get to the cause of this tho... Thanx Don

As a follow up to this posting I would like to relate my experience up to this time. The Arduino is controlling the kiln properly now that I am disconnected from the laptop computer. I am powering the Arduino from a9 volt power supply blister pack and it does the job quite well. The max board is powered from the Arduino. I no longer get bad readings from the max chip. I am presently adding refinements to the code to enhance the performance of my kiln during the firing of my pottery.